This invention relates to an apparatus and method for testing the mechanical endurance of a slide fastener by determining the number of cycles of opening and closing which the slide fastener is capable of undergoing while being subjected to preselected degrees of loading in both the transverse and longitudinal directions before jamming or other malfunctioning occurs.
It has been customary in the commercial testing of slide fasteners (zippers) to follow the procedures of A.S.T.M. Standard D2061. In that standard, zipper chains and scoops are tested with respect to crosswise strength by loading a one-inch section of a zipper in a tensile testing machine to destruction, with respect to scoop pull-off by pulling a single scoop from the bead at right angles to the stringer using a tensile testing machine fitted with a specially designed fixture, and with respect to scoop slippage by determining the ability of a scoop to resist longitudinal movement along the bead of the tape with a tensile testing machine fitted with a specially designed fixture.
Federal Specification V-F-106d, entitled "Fasteners, Slide, Interlocking" provides for endurance testing of the chain of a slide fastener on a machine equipped with a reciprocating arm arranged to move the slider back and forth upon the chain a minimum of 10,000 cycles at a uniform rate of between 45 and 60 complete cycles per minute. The slider moves over a distance of approximately 5 inches for fasteners 6 inches and over in length and over a distance equal to two-thirds of the length of fasteners under 6 inches long. The stringers of the chain are not loaded transversely, nor is the slide fastener loaded longitudinally during such endurance testing.
Since in the normal use of a slide fastener it is virtually inevitable that the slide fastener will be exposed to both transverse and longitudinal loadings of varying degrees, it is important to know how well a given slide fastener will stand up in actual use under conditions involving greater or lesser degrees of loading of the slide fastener both transversely and longitudinally.
It is, therefore, an object of the invention to provide an apparatus for determining the endurance of a slide fastener when the slide fastener is exposed to various degrees of loading both transversely and longitudinally thereof during operation of the slide fastener, including both opening and closing thereof.